The CFB boiler is a type of fluidized bed combus-tion boiler in which fuel particles are fluidized by the combustion air. As advantages, the fluidization rate is comparatively rapid, and a circulating circuit for collect-ing scattering particles is provided at the outlet of the combustion chamber. This combustion method has the following features.

1. High Fuel Adaptability
Because the combustion reaction proceeds in the entire furnace height direction and a circulating cir-cuit for the fluidized particles exists, the CFB boiler has a long reaction time of combustion. For this reason, its adaptability to diverse fuels is high, and mixed combustion of multiple fuels is easy. Its desic-cation capacity is also high due to the holding heat quantity of the fluidized particles, enabling direct feed of fuels with a high percentage of moisture con-tent without advance desiccation.
2. Low Environmental Load
For SOx, dry-type furnace desulfurization is pos-sible by direct injection of limestone into the furnace. Generation of thermal NOx is suppressed due to the comparatively low combustion temperature (850– 950°C), and fuel NOx is also reduced by multistage injection of combustion air.
3. Low Air-Ratio Combustion Possible
The excess air ratio can be set low because the rela-tive velocity between the fuel particles and combus-tion air is large due to high-speed fluidization, sup-porting a favorable solid-gaseous reaction.
4. Economical Equipment (Low Installation Cost) Because the environmental load is low and special flue gas treatment equipment is not necessary, the equipment composition can be simplified, reducing equipment costs.